This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The function of articular cartilage is to withstand high pressure, absorb shock and prevent the transmission of stress to the underlying bone. Osteoarthritis is a very common disease characterized by progressive degeneration of articular cartilage experienced as pain and disability. Early arthritis is typified by loss of the proteoglycan (PG) "springs" that allow for cartilage to absorb everyday mechanical stress. In the past, T1[unreadable] and sodium magnetic resonance imaging techniques have been used to study articular cartilage, which is sensitive to the concentration of proteoglycan in tissue. The purpose of the present study is to exploit inherent contrast with chemical exchange saturation transfer (CEST) technique and correlate with T1[unreadable] relaxometry in arthritic cartilage of human knees. These results will enable us to determine specificity of T1[unreadable] MRI towards PG in different conditions. With these studies, we hope to gain additional insight into the spatial distribution and progressive loss of PG in arthritis. These insights will be useful for the tracking of osteoarthritis and its treatments in affected patients. Future goal is to get co-registered CEST and T1[unreadable] In vivo images for detecting early Osteoarthritis for increased diagnostic reliability.